Abstract: Taking the Niulanjiang River basin as the study area, this research analyzed the spatiotemporal variation characteristics of water quality and revealed the response relationship between land use patterns and water quality in the Niulanjiang River basin using comprehensive water quality pollution indices and the optimal geographical detector model based on water quality monitoring and land use type data. The results showed that compared to the dry season, water pollution in the Niulanjiang River Basin was more severe during the wet season, with heavily polluted areas mainly concentrated in tributaries, and total phosphorus(TP) being the most significant contributor to water pollution. Water quality in the Niulanjiang River basin was primarily affected by the density of farmland, while factors such as the proportion of forestland, the density of construction land, diversity indices, and the proportion of grassland also had important impacts on water quality. Although seasonal variations could affect the explanatory power of most factors, the role of farmland density as a key factor remained unchanged. The overall pollution level of water quality in the study area was not determined by a single factor but influenced by the interaction of multiple factors. These interactions demonstrated high explanatory power for the degree of water pollution both in the wet and dry seasons, often exceeding the influence of individual factors. To improve water quality in the Niulanjiang River basin, it was recommended to strengthen monitoring and management, strictly control TP emissions, optimize land use, protect ecological resources, study seasonal impacts, establish a comprehensive management system, and formulate targeted measures.